Hydraulic control system



March 22, 1966 G. A. DRONE 3,241,461

HYDRAULIC CONTROL SYSTEM Filed Sept. 5, 1963 3 Sheets-Sheet 1 March 22, 1966 s. A. DRQNE 3,241,461

HYDRAULIC CONTROL SYSTEM Filed Sept. 5, 1963 3 Sheets-Sheet 2 HIGH SPEED LOWERING IN LOWER LOW SPEED LOWERING HlGH SPEED LOWERING IN FLOAT lmmkoh March 22, 1966 G. A. DRONE HYDRAULIC CONTROL SYSTEM Filed Sept. 5, 1963 3 Sheets-Sheet 3 NORMAL. FLOAT IQ W LOW SPEED RAISING HIGH SPEED RAISING aM vm/kok ,QM'OBM United States Patent 3,241,461 HYDRAULHJ CONTROL SYSTEM Gary A. Drone, Springfield, Ill., assignor to Allis- Cliaimers Manufacturing Company, Milwaukee, Wis. Filed dept. 3, 1963, Ser. No. 306,137 6 (Claims. (Cl. 91-436) This invention relates to improved hydraulic control system for a material handling mechanism such as a bulldozer tractor. More particularly, the invention relates to the addition of a novel flow control mechanism between a double acting jack and the control valve for operating the jack.

In providing a hydraulic control system for a material handling mechanism such as a bulldozer tractor, it is customary to provide a relatively large diameter hydraulic jack to provide the necessary down pressure on the blade to effectively penetrate the ground. Also, it is recognized that the larger the hydraulic jack used in such a control system, the slower it will move assuming the same source of pressure fluid is used. Further, it is desirable in manufacturing and selling construction equipment to provide machinery which gives maximum performance per dollar investment. Thus, increasing the size of the hydraulic pump, control valve and conduits to obtain more rapid operation of the jacks would necessarily increase the cost of the machinery. In order to obtain optimum performance of a bulldozer tractor and related equipment, I conceived of an improved fluid flow control arrangement whereby fluid is transferred from one end of the double acting hydraulic jack to the other under certain predetermined circumstances. In order to make the flow control mechanism an item of optional factory installed equipment and in order to make the addition readily available for use on equipment previously sold, I further conceived of a package arrangement for my flow control valve mechanism which may be added to existing hydraulic systems in an inexpensive and convenient manner.

It is an object of this invention to provide an improved hydraulic control system for a material handling mechanism whereby rapid operation of a hydraulically controlled implement or attachment is effected automatically under certain conditions.

It is a further object of this invention to provide a flow control mechanism for automatically bypassing fluid from one end of a double acting hydraulic jack to the other end when the flow from one end of the jack exceeds a predetermined rate and the pressure in said one end of the jack exceeds the pressure in the other end by a predetermined value.

It is a further object of this invention to provide an automatic flow control mechanism of the hereinbefore outlined type which does not interfere with the normal hold function of the hydraulic control system.

It is a further object of this invention to provide a conveniently packaged flow control mechanism for bypassing fluid from one end of a hydraulic double acting jack to the other end under the conditions hereinbefore set forth, which may be easily and economically added to the hydraulic system.

It is a further object of this invention to provide a hydraulic control system for an implement or attachment wherein the implement would be lowered at a high speed in either the lower or float condition of the control valve when the flow from one end of the jack reaches a predetermined rate and pressure in said one end of the jack exceeds the pressure in the other end by a predetermined value.

These and other objects and advantages of this invention will become apparent when the following description is read in conjunction with the drawings in which:

FIG. 1 is a view of the crawler tractor with a dozer attachment which includes the hydraulic control system of this invention;

FIG. 2 is a section view of the double acting hydraulic jack illustrated in FIG. 1 showing the flow control mechanism of this invention attached to the upper end of the jack;

FIG. 3 is a view taken along the lines III-III in FIG. 2;

FIG. 4 is a section view of the flow control mechanism of this invention shown in a position of high speed extension of the hydraulic jack which provides high speed lowering of the blade;

FIG. 5 is a schematic illustration of the hydraulic control system of this invention showing high speed lowering with the control valve in its lower position;

FIG. 6 is a schematic illustration of the hydraulic control of this invention showing low speed lowering with the control valve in its lower position;

FIG. 7 is a schematic illustration of the hydraulic control system of this invention showing high speed lowering with the control valve in its float position;

FIG. 8 is a schematic illustration of the hydraulic control system of this invention showing a normal float.

operation with the control valve in its float position.

FIG. 9 is a schematic illustration of the hydraulic control system of this invention showing low speed raising with the control valve in its raise position;

FIG. 10 is a schematic illustration of the hydraulic control system of this invention showing high speed raising with the control valve in its raise position; and

FIG. 11 is a view taken along the line XI-XI in FIG. 4.

In operation of a material handling mechanism such as a bulldozer tractor illustrated in FIG. 1, it is desirable at times to lower the bulldozer blade 11 quickly. The ordinary hydraulic control system does not permit lowering as fast as is desired in many instances.

The present invention solves this problem by adding a flow control mechanism 12 to the upper end of each of the pair of double acting hydraulic jacks 1.3 (only one of which is shown) which are interposed between the tractor 14 and the push beams 17 of the bulldozer attachment 16. The pushbeams 17, only one of which is illustrated,

are attached to the tractor 14 for vertical swinging movement about pivot connections 18 at opposite sides of the tractor. The source of pressure fluid is not illustrated in FIG. 1, however, it is schematically illustrated in FIGS. 5 through 10. The hydraulic pump supplying pressure fluid may be engine driven and the hydraulic control valve may be located convenient to the operators station 19.

In operating a bulldozer it is desirable to have a control valve, such as schematically illustrated in FIGS. 5 through 10, for controlling the blade attachment, which has raise, lower, hold and float positions. Also, in a number of operating conditions, it is desirable to lower the blade more rapidly than is permitted by placing the control valve in its lower or float positions. For instance, in dozing work, some time is saved by quickly lowering the blade. Also, in reforestation work the operator in dozing stumps in an area, where small seedling trees are also present, will find high speed lowering highly desirable. For instance, in the latter situation the crawler tractor must approach the stump with the blade raised so as to avoid injury to small seedling trees. Thus, as the stump to be excavated is approached, the operator wishes to quickly lower the blade to a condition wherein the cutting edge of the blade meets the bottom of the stump without the vehicle slowing its speed (thus using the momentum of the tractor as well as its engine power, to excavate the stump). Lowering speeds with conventional equipment are too slow to avoid injury to seedlings near the stump and thus a higher speed of lowering has been desired. The present invention satisfies this need in an economical and operationally satisfactory manner.

Referring to FIGS. 2 and 3, my flow control mechanism 12 includes a housing 21 which is inserted between the usual cylinder cap 23 and the upper closed end of the cylinder 24 of double acting jack 13. The cap 23 and housing 21 are secured by four cap screws 26 which extend through bores, not shown, in the cap and housing and have their lower ends threaded into drilled and tapped holes, not shown, in the upper end of the cylinder 24. Supply conduits 27, 28 extend from the cap 23 to a source of pressure fluid as will hereinafter be explained. Internal passages 29, 31 in cap 23 connect the conduits 27, 28, respectively, with downward opening ports 32, 33 on the bottom side of cap 23. Fluid supply port 34 in the upper end of the cylinder 24 provides an inlet for fluid to the upper end of hydraulic jack 13 and supply port 36, also in the upper end of the cylinder 24, is in communication with the lower end of the hydraulic jack 13 through appropriate fittings and a tube 37 which in effect is a continuation of conduit 28. The diameter of supply port 34 is larger than the diameter of port 32 and larger than the interior diameter of conduit 27.

Referring to FIG. 4, aligned bores 38, 39 form a first passage through housing 21, opposite ends of which are hydraulically in series with conduit 27. Opening 91 and bore 92 form a second passage through the housing 21, opposite ends of which are hydraulically in series with conduit 28. These first and second passages are interconnected by a bypass passage 53.

A double valve assembly 41 includes a pair of differential pressure valve spools 43, 51 which function automatically as hereninafter explained. A small diameter axially extending opening or hole 42 through spool 43 restricts fluid flow through conduit 28 in the direction from jack 13. Flow in the opposite direction however is not limited by restricted opening 42 but rather the valve member 43 will move downwardly from its restricted position to the unrestricted flow position illustrated in FIG. 10, when flow to jack 13 through conduit 28 exceeds a predetermined rate. The pressure area on the upper end of the one way restriction valve 43 is suflicently large and its biasing spring 44- sufliciently weak to permit substantially unrestricted flow of fluid to the jack 13 through conduit 28. The coil spring 44 also biases a concentrically arranged valve member 51 to its closed position, as shown in FIGS. 2, 6, 8, 9 and 10. Valve member 51 has an interior cylindrical sealing surface 52 in fluid sealing relation to cylindrical sealing surface 53 on valve member 43. When the cylindrical valve member 51 is in its seated position, its end surface 54 is in fluid tight sealing engagement with an angular flat sealing surface 56 formed on the bottom wall 22 of housing 21. Port 33 is in fluid communication with the top end of valve member 51 through recesses in the form of flutes 57 formed in the inner valve member 43. The flutes are more fully shown in FIG. 11, which is a top view of valve member 43,

When the rate of fluid flow from the bottom end of the ram exceeds a predetermined rate, the pressure differential acting upon valve member 51 will cause the valve to raise to the open position illustrated in FIG. 4 permitting fluid to flow from the lower end of the jack 13 to bypass passage 58 formed by walls 59. The bypass passage 58 serves as a bypass between the opposite ends of jack 13.

As illustrated in FIG. 4, the fluid pressure in the bottom end of the jack 13 is sufliciently greater than the fluid pressure in the upper end of the jack 13 to move the differential pressure valve member 61 upwardly to the open position illustrated in FIG. 4 in opposition to a biasing spring 62. Pressure acting on the upper end of the valve 61 is substantially the same as the pressure in the upper end of the jack 13 inasmuch as the diameter of the opening 63 in valve member 61 is at least as great as the interior diameter of conduit 27 and as illustrated is greater.

As shown in FIG. 2, the biasing spring 62 urges the valve member 61 to its seated position in which the annular seating surface 66 on the bottom of the valve member 51 is in fluid sealing engagement with the complementary sealing surface 67 on the bottom wall of the valve housing 21.

High speed lowering with control valve in lower As illustrated in FIG. 5, the manually operated control valve 71 is in its lower position and fluid from pump 72 is delivered through conduit 27 to the upper end of double acting jack 13. Fluid returning to reservoir 73 from the lower end of jack 13 through conduit 28 must pass through restricted opening 42 and upon the flow rate exceeding a predetermined value the pressure on the jack side of the valve member will exceed the pressure on the control valve side to a predetermined extent causing it to open and admit fluid to the bypass passage 53. As illustrated in FIG. 5, downward movement of the dozer attachment 16 is not opposed and gravity loading will cause the pressure in the bottom end of jack 13 to be greater than the pressure in its upper end. Upon the pressure in bypass passage 58, and hence in the bottom end of jack 13, exceeding the pressure in conduit 27 to a predetermined extent, the valve 61 will open in opposition to biasing spring 62. When the blade acts under the force of gravity upon the double acting jack 13, the supply pump will not supply fluid to the upper end of the jack sufliciently fast to maintain enough pressure on the upper side of the valve 61 to maintain it closed against pressure in the lower end of the jack acting in the bypass passage 58, upon the bottom of valve 61. Bypassing of fluid from the lower end to the upper end of the jack 13 is thus permitted and this results in a higher lowering speed than is conventionally obtainable with the same size jack, conduits, control valve and pump, but minus flow control mechanism 12. The size of openings 34, 33 permits adding part of the fluid flow from the bottom end of jack 13 to the pump delivery without undue restriction.

As shown in FIG. 5, the dozer attachment 16 is being lowered at high speed as the crawler tractor 14 is advancing toward a stump 76. The speed of the crawler tractor and the speed of lowering in the high speed lowering condition illustrated, will place the cutting edge at the bottom of the dozer blade 11 in contact with the base of the stump as indicated at 77. This is the approximate contact point that is desired for effective stumping operations. In reforestation work, it is desired to avoid injury if possible to small seedlings 78. In a conventional lowering system the speed of lowering would be considerably slower thereby forcing the operator to begin lowering the blade sufliciently early that in its slow descent it would inpure a greater number of seedlings. It is of course desired to have the tractor travel at a sufliciently fast speed to have the proper amount of tractor momentum available to add to engine power to most effectively cut and uproot the stump 76.

Low speed lowering wtih control valve in lower As shown in FIG. 6, the bulldozer blade 11 is engaged with the earth in an excavating position and the control valve 71 is in its lower position. In this condition the upper end of the jack .13 will be pressurized by fluid supplied by the pump 72 through control valve 71 and the conduit 27, and thus there is sufficient force on the upper end of flow control valve member 61 to maintain it in its seated position. Thus it is not possible to bypass fluid from the bottom end to the upper end of the jack 13 by way of the flow control mechanism 12. The speed of lowering, when a down pressure is exerted on the blade of the dozer, will be relatively slow because all fluid returning from the bottom end of the jack 13 is returned through the restriction in the form of opening 42, even if valve 51 should move to its bypass position. In power down operations, the operator does not desire a high speed blade movement and may actually feather the control valve to obtain a slow feeding of pressure fluid, to the upper end of the jack 13.

High speed lowering in float position of the control valve When operating in a float position of the control valve the blade will ride up over humps, such as 81 illustrated in FIG. 7, and then when the crawler track passes over the hump the blade 11 will be raised off the ground unless a high speed fluid transfer can be effected between the opposite ends of the jack 13. This is accomplished by my invention as illustrated in FIG. 7 wherein gravity loading of the jack 13 will force the oil from the bottom end of the jack at a sufiicient rate to cause valve member 51 to open permitting return fluid to flow to the bypass passage 58. Low pressure will exist in the upper end of jack 13, since it is connected to reservoir 73, and thus the pressure exerted by the fluid in bypass 58 will raise valve member 61 to its open position permitting the regenerative cincuit illustrated. This results in fast lowering of the blade permitting it to follow the contour of the land rather than being held above the ground as has heretofore occurred using conventional hydraulic control apparatus.

Normal float operation The flow control mechanism 12 will also permit the blade to operate in a normal float condition when the control valve is in its float position as illustrated in FIG. 8. When the tractor is traversing a relatively fiat or gradually sloping contour, the return flow from the bottom of jack 13 will not be sufficient to open valve 51 and thus valve 61 will also remain closed.

Low speed raising with the control valve in its raised position As illustrated in FIG. 9, the control valve is in its raise position and either the pump 72 is delivering fluid at a low rate or the control valve is being feathered to limit t flow through the valve to conduit 28 and the flow through opening 42 is consequently not great enough to cause a differential in pressure on valve member 43. Thus the valve member 43 remains in its low flow rate position as illustrated.

High speed raising with the control valve in its raised position i As illustrated in FIG. 10, the rate of fluid flowing in conduit 28 is sufliciently great to cause a predetermined pressure differential across valve 43 thereby causing it to move against the biasing action of spring 44 to its high flow rate position illustrated wherein cylindrical sealing surfaces 53 no longer engages with cylindrical surface 52 and flutes 57 permit a substantially unrestricted opening to the bottom port 36.

The raising speed is responsive to pump delivery and valve member 43 ofiers very little resistance to flow to the jack. In effect, valve member 43 affords only one way restriction to fluid flow.

From the foregoing description it is evident that I have provided an extremely useful hydraulic control system for a vertically adjustable excavating attachment of a material handling vehicle and particularly a novel flow control means for automatically effecting high speed lowering of the attachment in lower and float positions of the control valve when the rate of flow from the lower end of the attachment lifting jack exceeds a predetermined value and the fluid pressure in the lower end of the jack exceeds the fluid pressure in its upper end to a predetermined extent.

The flow control mechanism 12 conveniently fits between the closed end of the cylinder 24 and the conventional cap 23 thus permitting convenient modernization of equipment previously sold, Also the flow control mechanism 12 can be offered as optional equipment with no costly modifications being required. My arrangement of the differential pressure valve spools or members 43, 51, 61 with control fluid flow therethrough to the jack, provides a compact package requiring a minimum of space. Also the use of a single spring 44 for biasing both the one way restriction valve member 43 and valve member 51 eifects a savings in cost as well as space. The addition of my flow control mechanism 12 does not interfere with the normal hold operation of the hydraulic control system which is achieved when the control valve 71 is moved to its hold position, not shown.

The embodiments of the invention for which an exclusive property or privilege is claimed are defined as follows:

1. A hydraulic control system for a material handling mechanism, comprising:

a double acting jack,

a source of fluid pressure including a control valve having raise, lower and float positions,

a pair of fluid supply conduits operatively connecting said control valve to opposite ends of said jack, respectively,

a bypass passage inter-connecting said conduits,

and means controlling fluid flow through said bypass passage including a first differential pressure valve in said bypass passage biased to a closed position in which fluid flow through said bypass passage is prevented, said first valve moving to an open position in which fluid is permitted to flow in said bypass passage when the flow from said jack through said one conduit exceeds a predetermined rate,

and a second diiferential pressure valve in said bypass passage biased to a closed position in which fluid is prevented from flowing through said bypass passage, said second valve moving to an open position in which fluid is permitted to flow in said bypass passage upon the fluid pressure in said one conduit exceeding the fluid pressure in said other conduit by a predetermined value and said second valve having a central opening therethrough permitting free fluid flow therethrough between said control valve and jack by way of said other conduit.

2. A hydraulic control system for a material handling mechanism, comprising:

a double acting hydraulic jack a source of fluid pressure including a control valve having raise, lower and hold positions,

a pair of fluid supply conduits operatively connecting said control valve to opposite ends of said jack, respectively,

a bypass passage interconnecting said conduits,

flow control means blocking flow of fluid through said bypass passage when the rate of flow from said jack to said control valve through one of said conduits is below a predetermined value and opening to permit flow of fluid through said bypass passage when said rate of flow exceeds said predetermined value and a spool valve member in said bypass passage biased to a closed position in which it blocks flow of fluid through said bypass passage and shifted to an open position in which fluid is permitted to flow in said bypass passage when the pressure in said one conduit exceeds the pressure in the other of said conduits to a predetermined extent, said spool valve member having a central opening therethrough whereby fluid flow ing between said control valve and jack through said other conduit flows freely through said opening.

3. The structure set forth in claim 2 wherein said flow control means includes a flow restricting means in said one conduit between said bypass passage and said control valve and a differential pressure valve in said bypass passage sensitive at its opposite ends to the fluid pressure in said one conduit on the opposite sides of said flow restricting means.

4. A hydraulic control system for a material handling mechanism, comprising:

a double acting hydraulic jack,

a source of fluid pressure including a control valve having raise, lower and float positions,

a pair of fluid supply conduits operatively connecting said control valve to opposite ends of said jack, respectively,

a bypass passage interconnecting said conduits,

and a flow control mechanism including a differential pressure valve biased to a closed position in which fluid flow in said bypass passage between said conduits is prevented and having an open position in which it permits fluid flow in said bypass passage,

flow control means restricting fluid flow in said one conduit to a low rate of flow from one side of said differential pressure valve to the other side thereof in the direction from said jack in all positions of said differential valve and permitting a high rate of flow in the opposite direction,

said differential valve moving to its open position when the flow rate in said one conduit from said jack is great enough to create a predetermined pressure differential across said differential pressure valve,

and an automatic operating valve in said bypass passage biased to a closed position in which fluid is prevented from flowing between said conduits through said bypass passage, said automatic operating valve moving to an open position permitting fluid flow through said bypass passage upon the fluid pressure in said one conduit exceeding the fluid pressure in the other of said conduits by a predetermined value.

5. A flow control mechanism adapted for insertion in a pair of fluid conduits supplying a hydraulic jack, comprising:

a housing having walls defining a first passage extending through said housing terminating at opposite ends in openings adapted for connection in series with one of said conduits,

a second passage extending through said housing terminating at opposite ends in openings adapted for connection in series with the other of said conduits, and

a bypass passage interconnecting said first and second passages,

a first differential pressure valve spool positioned in said first passage having an opening axially therethrough permitting substantially unrestricted fluid flow therethrough,

means biasing said first differential pressure valve spool to a closed position in which it blocks fluid flow through said bypass passage,

a second differential pressure valve spool positioned in said second passage having a bore axially therethrough,

a third differential pressure valve spool reciprocably mounted in said bore and having a restricted opening axially therethrough and a biasing spring interposed between said second and third spools biasing said second spool to a closed position in which it prevents fluid flow through said bypass passage and biasing said third spool to a restricted flow position in which all flow through said second passage passes through said restricted opening,

said third spool being shiftable to an open position in which fluid flow through said second passage is substantially unrestricted when the pressure on the jack side of said third spool is slightly less than the pressure on the opposite side thereof,

said second spool moving to an open position permitting fluid flow in said bypass passage when the rate of flow from said jack through said restricted opening exceeds a predetermined value and said first spool moving to an open position when the fluid pressure in said second passage, on the jack side of said third spool, exceeds the fluid pressure in said first passage by a predetermined value.

6. The structure set forth in claim 4 wherein said flow control means includes a valve element reciprocably mounted in said differential valve and having a small diameter axial opening therethrough.

References Cited by the Examiner UNITED STATES PATENTS 5/1959 Rogers 91-420 4/1964 Allen 91-430 X 

1. A HYDRAULIC CONTROL SYSTEM FOR A MATERIAL HANDLING MECHANISM, A COMPRISING: A DOUBLE ACTING JACK, A SOURCE OF FLUID PRESSURE INCLUDING A CONTROL VALVE HAVING RAISE, LOWER AND FLOAT POSITIONS, A PAIR OF FLUID SUPPLY CONDUITS OPERATIVELY CONNECTING SAID CONTROL VALVE TO OPPOSITE ENDS OF SAID JACK, RESPECTIVELY, A BYPASS PASSAGE INTERCONNECTING SAID CONDUITS, AND MEANS CONTROLLING FLUID FLOW THROUGH SAID BYPASS PASSAGE INCLUDING A FIRST DIFFERENTIAL PRESSURE VALVE IN SAID BYPASS PASSAGE BIASED TO A CLOSED POSITION IN WHICH FLUID FLOW THROUGH SAID BYPASS PASSAGE IS PREVENTED, SAID FIRST VALVE MOVING TO AN OPEN POSITION IN WHICH FLUID IS PERMITTED TO FLOW IN SAID BYPASS PASSAGE WHEN THE FLOW FROM SAID JACK THROUGH SAID ONE CONDUIT EXCEEDS A PREDETERMINED RATE, 